Thermoplastic polyester resins, such as poly-ethylene terephthalate and poly-butylene terephthalate, or polyacetal resins have been used in a number of end-use applications as engineering resins in recent years since they exhibit superior mechanical and electric properties, heat and chemical resistances and workability. And, there is a tendency that these resins will be used under still more severe conditions with an expansion of their end-use applications. As such, these resins will be required to exhibit improved properties for many such applications. Some of these properties are improved frictional and abrasive characteristics, long-term durability of such improved frictional and abrasive characteristics, reduction of frictional noise due to the wear part's sliding or the like, (such as sliding members and actuator members, used in cars, electric and electronic products and the like).
For example, it is known that (1) solid lubricants, such as molybdenum disulfide and graphite, (2) powdery and fibrous poly-tetrafluoroethylene resin, (3) liquid or semi-solid lubricants, such as petroleum lubricating oils, synthetic lubricating oils, aliphatic alcohols or their esters, and the like may be added as a means of improving the frictional and abrasive characteristics of thermoplastic resins. It goes without saying that some improvements of the frictional and abrasive characteristics by these known methods ensues, and in particular the requirements can be met in those situations where a part formed of such resins is used only for a short time under sliding conditions at relatively low speed and load. However, problems have occurred in that the frictional characteristics become insufficient as the sliding speed and load increase. The frictional characteristics therefore significantly deteriorated over time in use even under sliding conditions of low speeds and loads. In addition, it is known that polyethylene, polytetrafluoroethylene and the like may be added to soften resins, and has been generally used as a method of improving frictional noise when sliding. However, with this known technique, a silencing property capable of meeting the desired requirements cannot always be attained. In addition, problems have occurred in that physical properties, such as mechanical strength, decrease.
As above described, according to the conventional known techniques, the requirements, which are being increasingly made more severe, cannot be met with respect to frictional and abrasive characteristics, in particular such characteristics under high speed and a high load sliding conditions or in terms of long-term anti-friction characteristics or silencing characteristics when sliding. Accordingly, improvements in these areas have been needed.